Computer system for performing adaptive interrupt control and method for controlling interrupt thereof

ABSTRACT

A computer system includes a host and a storage device. The host provides an input/output request (IO request). The storage device receives the request from the host and sends an interrupt informing input/output completion (IO completion) to the host after completing the IO request. The host adjusts the number of generated interrupts of the storage device using the number of delayed IOs. The computer system may adaptively control interrupt generation of the storage device based on a load status of a CPU or the number of delayed IOs. The interrupt generation of the storage device may be adjusted to obtain a CPU gain without loss of performance or processing time of the computer system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. non-provisional patent application claims priority under 35USC § 119 to Korean Patent Application No. 10-2016-0061337, filed on May19, 2016, the entirety of which is hereby incorporated by reference.

BACKGROUND

Example embodiments of inventive concepts relate generally to computersystems and/or methods of controlling same. For example, at least someexample embodiments relate to a computer system for performing adaptiveinterrupt control and/or a method for controlling an interrupt thereof.

A computer system may include a host and a storage device. The host maybe a computer mainframe or a server system. The storage device may beelectrically connected to the host. The storage device may receive aninput/output (IO) request from the host and process the received IOrequest. The storage device completes the IO request and may provide aninterrupt to the host, thus informing the host of the IO completion.

A conventional storage device may have a relatively lower dataprocessing speed than a data processing speed of the host. Accordingly,while the storage device processes an IO request, the host may executeanother program to enhance perform of a system. When the host receivesthe interrupt, via the IO request from the storage device, whileexecuting another program, the host may stop the program that is beingexecuted and process the interrupt. After processing the interrupt, thehost may recover the stopped program and execute the recovered program.

With the advance in semiconductor manufacturing technology, input/outputprocessing speed of a storage device has improved to come close to thedata processing speed of the host. As the data processing speed of thestorage device is improved, the storage device may generate too manyinterrupts, thus degrading performance of the computer system.

SUMMARY

Example embodiments relate to a computer system and/or a method forcontrolling an interrupt of the computer system.

A computer system according to example embodiments of inventive conceptsincludes a host and a storage device. The storage device may beconfigured to receive an input/output (IO) request, and to send aninterrupt informing input/output (IO) completion after completing the IOrequest; and the host may be configured to generate the IO request, andto adjust a number of generated interrupts of the storage device basedon a number of delayed IOs.

A computer system according to example embodiments of inventive conceptsincludes a first storage device configured to receive a firstinput/output (IO) request, and to send an interrupt informing a first IOcompletion after completing the first IO request; a second storagedevice configured to receive a second IO request, and to send aninterrupt informing a second IO completion after completing the secondIO request; and a host including a first processor and a secondprocessor, the host configured to, perform adaptive interrupt control ofthe first processor by adjusting a number of generated interrupts of thefirst storage device based on a number of delayed IOs between the hostand the first storage device, and perform adaptive interrupt control ofthe second processor by adjusting a number of generated interrupts ofthe second storage device based on a number of delayed IOs between thehost and the second storage device.

A method of controlling an interrupt of a storage device connected to ahost according to example embodiments of inventive concepts includesreceiving an input/output (IO) request from the host; adjusting a numberof generated interrupts of the storage device based on a number ofdelayed IOs between the host and the storage device; completing the IOrequest received from the host; and sending an interrupt indicating aninput/output (IO) completion to the host based on the adjusted number ofthe generated interrupts.

A host device according to example embodiments of the inventive conceptsmay include an interface configured to communicate with a storagedevice; and a processor configured to activate adaptive interruptcontrol (AIC) based on one or more of an idle ratio associated with thehost device and a number of interrupts pending at the host device, theAIC instructing the storage device to reduce the number of interruptstransmitted to the host device.

BRIEF DESCRIPTION OF THE DRAWINGS

The forgoing and other features of example embodiments of the inventiveconcepts will be described below in more detail with reference to theaccompanying drawings of non-limiting example embodiments of inventiveconcepts in which like reference characters refer to like partsthroughout the different views. The drawings are not necessarily toscale, emphasis instead being placed upon illustrating principles ofinventive concepts. In the drawings:

FIG. 1 is a block diagram of a computer system;

FIG. 2 is a flowchart summarizing operation of the computer system shownin FIG. 1;

FIG. 3 is a block diagram of a computer system according to exampleembodiments of inventive concepts;

FIG. 4 is a block diagram of an AIC unit shown in FIG. 3;

FIG. 5 is a flowchart summarizing operation of a load watcher shown inFIG. 4;

FIG. 6 is a flowchart summarizing operation of a decision maker shown inFIG. 4;

FIGS. 7 and 8 are flowcharts summarizing operations of an interruptcontroller shown in FIG. 4, respectively;

FIG. 9 is a conceptual diagram illustrating operations of a submissionqueue and a completion queue shown in FIG. 4;

FIG. 10 is a table defining a delay IO shown in FIG. 9;

FIG. 11 is a block diagram of a computer system according to exampleembodiments of inventive concepts; and

FIG. 12 is a block diagram of a computer system according to exampleembodiments of inventive concepts.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of a computer system 100 according to exampleembodiments.

Referring to FIG. 1, as illustrated, the computer system 100 includes ahost 110 and a storage device 120. The host 110 may be an electronicdevice such as a server computer, a desktop computer, a laptop computer,and/or a table personal computer (PC). The host 110 may be connected toperipheral devices (e.g., a keyboard, a mouse, a printer, a display,etc.) other than the storage device 120.

The host 110 may process data and may make a data input/output requestto the storage device 120. Hereinafter, a series of operations for thehost 110 to make the data input/output request to the storage device 120will be simply referred to as “IO request”.

The storage device 120 may be electrically connected to the host 110.The storage device 120 may be a storage medium based on a flash memorysuch as a solid state drive (SSD), a personal computer memory cardinternational association (PCMCIA), a compact flash card (CF), a smartmedia card (SM or SMC), a memory stick, a multimedia card (MMC, RS-MMCor MMCmicro), an SD card (SD, miniSD, microSD or SDHC), a universalserial bus (USB) memory card, and/or a universal flash storage (UFS).The storage device 120 may be implemented using an embedded memory suchas an embedded multimedia card (eMNIC), a UFS, and/or a perfect page new(PPN) memory.

Continuing to refer to FIG. 1, the host 110 may make a data input/outputrequest (IO request) to the storage device 120. For example, the host110 may provide a write request to write data into the storage device120 or a read request to read data from the storage device 120. Thestorage device 120 may receive the IO request and may process thereceived IO request. The storage device 120 may complete the IO requestand may generate an interrupt. The storage device 120 may inform thehost 110 of IO completion through the interrupt.

FIG. 2 is a flowchart summarizing operation of the computer system 100shown in FIG. 1.

Referring to FIG. 2, in operation S110, the host 110 may make an IOrequest to write data into the storage device 120 or to read data fromthe storage device 120. For example, when the host 110 wishes to storean image file in the storage device 120, the host 110 may make a writerequest to the storage device 120. When the host 110 wishes to read or,alternatively, to view) an image stored in the storage device 120, thehost 110 may make a read request.

In operation S120, the storage device 120 may receive the IO requestfrom the host 110 and may execute the IO request. The storage device 120may include a first storage medium having high input/output processingspeed and a second storage medium for retaining data for a long periodof time. The first storage medium may be implemented using a randomaccessible volatile memory (e.g., DRAM) or a nonvolatile memory (e.g.,PRAM or MRAM). The second storage medium may be implemented using anonvolatile memory such as a flash memory. However, example embodimentsare not limited thereto.

In the case of a write request, the storage device 120 may receive thewrite request and may store data in the first storage medium. Thestorage device 120 may internally move the data stored in the firststorage medium to the second storage medium. The storage device 120 mayperform the operation of moving the data to the second storage mediumduring an idle time or a background operation.

In operation S130, the storage device 120 may complete the IO requestand may provide the interrupt to the host 110. For example, when thedata received from the host 110 is stored in the first storage medium,the storage device 120 may generate IO completion. That is, even whenthe storage device 120 has not completed internally moving the data tothe second storage medium, the storage device 120 may process the IOcompletion. The storage device 120 may provide an interrupt to the host110 to inform the IO completion.

In operation S140, the host 110 receives the interrupt from the storagedevice 120 and saves a context that is being executed.

In operation S150, after saving the context that is being executed, thehost 110 processes the interrupt.

In operation S160, after processing the interrupt, the host IO restoresthe saved context.

In operation S170, after restoring the context, the host 110 mayreadjust a schedule.

The IO processing speed of the storage device 120 may be lower than thatof the host 110. While the storage device 120 processes the IO request,the host 110 waits until the storage device 120 processes the IOrequest. To lower the overhead, the host 110 may execute another contextwhile the storage device 120 executes the IO request. When the host 110receives the interrupt while executing the context, the host 110 savesthe context that is being executed and processes the interrupt.

The computer system 100 shown in FIG. 1 may reduce the overhead of thehost 110 when the IO processing speed of the storage device 120 is low.That is, the host 110 may execute another context using the interruptwhile the storage device 120 executes the request.

FIG. 3 is a block diagram of a computer system 1000 according to exampleembodiments of inventive concepts.

Referring to FIG. 3, as illustrated, the computer system 1000 includes ahost 1100, a storage device 1200, and an input/output (IO) device 1300.The host 1100 may be connected to the storage device 1200 and the IOdevice 1300 through an external bus. The storage device 1200 may be astorage medium operating at high speed such as a solid state device(SSD). The IO device 1300 may be a device used to input or output datasuch as a keyboard, a mouse, a monitor, and a printer.

Still referring to FIG. 3, the host 1100 may include a centralprocessing unit (CPU) 1110, a random access memory (RAM) 1120, anadaptive interrupt control (AIC) unit 1130, and an external memoryinterface 1140.

The CPU 1110 executes a program command of the host 1100. That is, theCPU 1110 may interpret the program command and may control the overalloperation of the host 1100 according to the interpreted program command.Additionally, the CPU 1110 may perform not only arithmetic operationssuch as addition, subtraction, multiplication, and division but alsological operations such as AND, OR, NOT, and XOR.

Performance of the CPU 1110 may be measured based on the number of IOoperations performed per second. Processing speed of the CPU 1110 may beexpressed by Hertz (Hz) that is a unit of frequency. The greater afrequency value, the higher speed of the CPU 1110. In addition, theperformance of the CPU 1110 may be evaluated based on the number ofcores included in the CPU 1110. As a multi-core CPU emerges, theprocessing speed of the CPU 1110 may become much higher.

The RAM 1120 may be used to perform an arithmetic operation of the CPU1110 or to drive an operating system (OS) or a device driver. The RAM1120 may be used as a main memory device. The RAM 1120 may beimplemented using a volatile memory such as DRAM or SRAM. In addition,the RAM 1120 may be implemented using a nonvolatile memory such as PRAMor MRAM.

The AIC unit 1130 may include a device driver to drive the storagedevice 1200. The device driver may be downloaded through Internet in theform of software or firmware or may be executed through a storage medium(e.g., CD or USB memory). Alternatively, the device driver may be loadedto the host 1100 from the storage device 1200 or a non-volatile memoryassociated with the host 1100 (not shown). The device driver may beexecuted by the CPU 1110, to configure the CPU 1110 to perform theoperations of the AIC unit 1130.

The AIC unit 1130 may adjust interrupt generation of the storage device1200. For example, the AIC unit 1130 may sense an IO load of the CPU1110 to adjust interrupt generation. Additionally, the AIC unit 1130 mayadjust interrupt generation through delay IO during an IO operation ofthe host 1100 and the storage device 1200. The configuration andoperation principle of the AIC unit 1130 will be described below indetail.

The external memory interface 1140 may be connected to the storagedevice 1200 through an external bus. The external memory interface 1140may have various interface schemes. For example, the external memoryinterface 1140 may exchange data with the storage device 1200 through astandard such as SATA, PATA, eMMC, UFS, USB, PCIe, and NVMe.

The storage device 1200 may be classified into a high-speed storagedevice and a low-speed storage device according to data IO speed. Thedata IO speed of the storage device 1200 may be decided according totype and interface of a storage medium. In general, the high-speedstorage device may be based on a flash memory and the low-speed storagedevice may be based on a magnetic disk.

When the storage device 1200 inputs and outputs data at high speed, toomany interrupts may be generated. When too many interrupts aregenerated, excess overhead may occur in the host 1100. For example, itwill be assumed that the storage device 1200 has input/output speed of 1mega IO per second (1 M IOPS). That is, the storage device 1200 mayarithmetically generate one million interrupts per second. When onemillion interrupts are generated per second in the storage device 1200,the host 1100 performs a series of operations to stop a context that isbeing executed, process the interrupt, and recover the context, onemillion times.

As the storage device 1200 operates at high speed, an overhead caused byan interrupt is increasing. For this reason, in a Linux system, aspecific CPU cycle is occupied for tens of seconds to process only aninterrupt and thus a soft lockup bug occurs. Due to an interrupt that istoo frequently generated in a high-speed storage device, performance ofthe computer system 1000 may be degraded.

The computer system 1000 may adaptively control interrupt generation ofthe storage device 1200 through the AIC unit 1130 based on a load statusof a CPU and/or the number of delayed IOs. The interrupt generation ofthe storage device 1200 may be adjusted to secure a CPU gain withoutloss of the performance or processing time of the computer system 1000.

FIG. 4 is a block diagram of the AIC unit 1130 shown in FIG. 3. Asdiscussed above, in some example embodiments, the CPU 1110 may execute asoftware module such that the CPU 1110 performs the operations of theAIC unit 1130 to control the storage device 1200. In other exampleembodiments, the functions of the AIC unit 1130 may be performed by adedicated circuit included in the host 1100. The storage device 1200 maybe a high-speed storage device based on a flash memory. For example, thestorage device 1200 may be an NVMe SSD.

Referring to FIG. 4, the AIC unit 1130 includes a load watcher 1131decision maker 1132, and an interrupt controller 1133.

The AIC unit 1130 may watch an IO load of the CPU 1110 to adaptivelycontrol interrupt generation during an IO operation of the host 1100 andthe storage device 1200. Thus, the computer system 1000 may reduce aninterrupt processing load of the host 1100 and may improve a cycle gainof the CPU 1110. Moreover, the computer system 1000 may decrease thenumber of generated interrupts to prevent degradation in IO performanceor delay of required processing time resulting from IO completionprocessing time delay.

The load watcher 1131 may periodically check a CPU load status. The loadwatcher 1131 may check the CPU load status after dividing the CPU loadstatus into a user mode, a system mode, an IO pending mode, and an idlestate mode. For example, the load watcher 1131 may activate adaptiveinterrupt control (AIC) using an idle ratio.

The load watcher 1131 may activate the AIC by comparing the idle ratiowith a threshold. For example, the load watcher 1131 may activate theAIC when the idle ratio is lower than the threshold (e.g., 10 percent).In contrast, the load watcher 1131 may deactivate the AIC when the idleratio is higher than the threshold (e.g., 10 percent).

The decision maker 1132 may control interrupt generation of the storagedevice 1200. When the host 1100 desires to control an interrupt of thestorage device 1200, the decision maker 1132 may determine an interruptcontrol level (ICL). The decision maker 1132 may determine the ICL usingdelayed IO. The delayed IO may be obtained using submission IO in thehost 1100 and completion IO in the storage device 1200.

The decision maker 11321 may calculate the number of delayed IOs basedon the IO submitted in the host 1100 (hereinafter referred to as “IOsq”)at a specific point of time and IO completed in the storage device 1200(hereinafter referred to as “IOcq”) at the specific point of time. Inexample embodiments, the number of delayed IOs may be calculated usingone of the IOsq and the IOcq or a sum or a difference thereof. Forexample, the decision maker 1132 may calculate the number of delayed IOsusing a difference between the IOsq and the IOcq. The delayed numbermeans the number of IOs that are currently pending in the computersystem 1000.

The decision maker 1132 may decide an interrupt control level ICL basedon the number of delayed IOs. The decision maker 1132 may use a decisionfunction for deciding the interrupt control level ICL. The decisionfunction may be defined in various manners. For example, the decisionfunction may be decided by dividing the number of delayed IOs in half.The decision function may decide the ICL by performing both anarithmetic operation and a modular operation. Alternatively, thedecision function may decide the interrupt control level ICL byperforming both an arithmetic operation and a modular operation on thenumber of delayed IOs.

When the decision maker 1132 changes the interrupt control level ICL toooften, IO performance between the host 1100 and the storage device 1200may be degraded. To prevent the degradation in IO performance, theinterrupt control level ICL may be adjusted to a fixed window size usingthe modular operation. To achieve this, a desired (or, alternatively, apredetermined) protocol is used between the host 1100 and the storagedevice 1200 to perform adaptive interrupt control AIC. For example, anNVMe may set up a protocol through Interrupt Coalescing/Interrupt VectorConfiguration Admin Command (Set/Get Feature 0x8, 0x9).

The decision maker 1132 may decide an interrupt control level ICL toreduce interrupt generation of the storage device 1200. For example,assuming that the interrupt control level ICL is 24, the storage device1200 may omit interrupt generation of 23 times and may generate aninterrupt only once. Accordingly, the decision maker 1132 may reduceinterrupt generation and prevent interrupt processing time delay.

The interrupt controller 1133 may receive the interrupt control levelICL from the decision maker 1132 and may provide an interrupt controlcommand CTRL to the storage device 1200. The interrupt controller 1133may increase or decrease the number of generated interrupts of thestorage device 1200.

Still referring to FIG. 4, the AIC unit 1130 may include a submissionqueue (SQ) 1134 and a completion queue (CQ) 1135. In some exampleembodiments, the submission queue 1134 may be included in the AIC unit1130. The submission queue 1134 and the completion queue 1135 may bedriven by the RAM 1120 (see FIG. 3) of the host 1100.

The submission queue 1134 may store IO requests provided form the CPU1110 and may sequentially provide the stored IO requests to the storagedevice 1200. The submission queue 1134 may store the IO request in theRAM 1120 (see FIG. 3). On the other hand, the completion queue 1135 maysequentially store IO requests completed in the storage device 1200. Thecompletion queue 1135 may receive an interrupt IO completion from thestorage device 1200 and may store the completed IO request. Thecompletion queue 1135 may store the IO completion in the RAM 1120. Thestorage device 1200 may receive the interrupt control command CTRL andmay generate an interrupt according to the interrupt control level ICL.

FIG. 5 is a flowchart summarizing operation of the load watcher 1131shown in FIG. 4.

Referring to FIG. 5, as discussed above, in some example embodiments,the CPU 1110 may execute a software module such that the CPU 1110performs the operations of the AIC unit 1130 including the load watcher1131. In other example embodiments, the functions of the AIC unit 1130may be performed by a dedicated circuit included in the host 1100.

In operation S210, the load watcher 1131 checks a load status of acurrent CPU 1110. The load watcher 1131 may receive IO information andmay periodically check the load status.

In operation S220, the load watcher 1131 may calculate an idle ratio ofthe CPU 1110. A load status of the CPU 1110 may be divided into a usermode, a system mode, an IO pending mode, and an idle state mode. An idleratio of a CPU means a ratio of an idle state to the entire load statusof the CPU. The AIC unit 1130 may activate adaptive interrupt control(AIC) based on the idle ratio.

In operation S230, the load watcher 1131 compares the idle ratio with athreshold. For example, the load watcher 1131 may determine whether theidle ratio is lower than the threshold. When the idle ratio is higherthan or equal to the threshold (No), the load watcher 1131 may notperform the AIC. If the adaptive interrupt control is being performed,the load watcher 1131 may deactivate the adaptive interrupt control.Meanwhile, when the idle ratio is lower than the threshold (Yes), theload watcher 1131 proceeds to operation S240.

In operation S240, the load watcher 1131 may activate the AIC when theidle ratio is lower than the threshold. For example, the load watcher1131 may activate the AIC when the idle ratio is lower than thethreshold by 10 percent. The load watcher 1131 may provide a signal foractivating the AIC to the decision maker 1132.

FIG. 6 is a flowchart summarizing operation of the decision maker 1132shown in FIG. 4.

Referring to FIG. 6, as discussed above, in some example embodiments,the CPU 1110 may execute a software module such that the CPU 1110performs the operations of the AIC unit 1130 including the decisionmaker 1132. In other example embodiments, the functions of the AIC unit1130 may be performed by a dedicated circuit included in the host 1100.

In operation S310, the decision maker 1132 may obtain the number ofpending delayed IOs. The decision maker 1132 may calculate the number ofthe delayed IOs using a submission IO IOsq and a completion IO IOcq. Forexample, the decision maker 1132 may calculate the number of the delayedIOs using a difference between the IOsq and the IOcq. The number of thedelayed IOs means the number of IOs that waits for processing in thecomputer system 1000.

In operation S320, the decision maker 1132 calculates an interruptcontrol level ICL based on the number of the delayed IOs. The interruptcontrol level ICL may be obtained by a desired (or, alternatively, apredetermined) decision function. For example, it will be assumed thatthe decision function is half the number of the delayed IOs. When theIOsq is 100 and IOcq is 10, the number of the delayed IOs is 90 that isa difference between the IOsq and the IOcq. Accordingly, the interruptcontrol level ICL is calculated as 45 by the decision function. When theinterrupt control level ICL is 45, the storage device 1200 omitsinterrupt generation of 44 times and generates an interrupt once.

In operation S330, the decision maker 1132 compares the interruptcontrol level ICL with a threshold level. The decision maker 1132 mayperform operation S330 when a modular operation is applied in operationS320. The decision maker 1132 may adjust the ICL to a fixed window sizeusing the modular operation. The decision maker 1132 determines whetherthe ICL is higher than the threshold level. When the ICL is lower thanor equal to the threshold level (No), the decision maker 1132 may notperform the adaptive interrupt control (AIC). In contrast, when the ICLis higher than the threshold level (Yes), the decision maker 1132proceeds to operation S340.

In operation S340, the decision maker 1132 may enable the adaptiveinterrupt control (AIC). For example, the decision maker 1132 mayprovide an interrupt control command CTRL to the storage device 1200when the interrupt control level ICL is higher than the threshold level.

FIGS. 7 and 8 are flowcharts summarizing operations of the interruptcontroller 1133 shown in FIG. 4. FIG. 7 illustrates an example in whichthe interrupt controller 1133 performs adaptive interrupt control (AIC)based on a load status of a CPU and the number of pending IOs, and FIG.8 illustrates an example in which the interrupt controller 1133 performsAIC based on the number of pending ICs.

Referring to FIG. 7, as discussed above, in some example embodiments,the CPU 1110 may execute a software module such that the CPU 1110performs the operations of the AIC unit 1130 including the interruptcontroller 1133. In other example embodiments, the functions of the AICunit 1130 may be performed by a dedicated circuit included in the host1100.

in operation S410, the interrupt controller 1133 determines whether theAIC is activated. As described in operation S230 of FIG. 5, activationof the AIC may be determined depending on whether a CPU idle ratio ishigher than a threshold. When the AIC is not activated, the interruptcontroller 1133 may not provide an interrupt control command CTRL to thestorage device 1200. Meanwhile, when the AIC is activated, the flowproceeds to S420.

In operation S420, the interrupt controller 1133 may determine whetherthe AIC is enabled. As described in operation S330 of FIG. 6, enablementof the AIC may be determined depending on whether the interrupt controllevel (ICL) is higher than a threshold. When the AIC is enabled, theflow proceeds to operation S430.

In operation S430, the interrupt controller 1133 sends the interruptcontrol command CTRL to the storage device 1200. The interruptcontroller 1133 may provide the interrupt control command CTRL, to thestorage device 1200 to adjust the number of generated interrupts.

According to the operation method of the interrupt controller 133 shownin FIG. 7, interrupt generation of the storage device 1200 may beadaptively controlled based on a load status of a CPU and the number ofdelayed IOs. The interrupt generation of the storage device 1200 may beadjusted to secure a CPU gain without loss of performance or processingtime of the computer system 1000.

Referring to FIG. 8, in operation S510, the interrupt controller 1133determines whether the AIC is enabled. The determination may be made bycomparing an interrupt control level ICL with a threshold level. Whenthe AIC is not enabled, the interrupt controller 1133 may not providethe interrupt control command CTRL to the storage device 1200.

In operation S520, when the AIC is enabled, the interrupt controller1133 sends the interrupt control command CTRL to the storage device1200. The interrupt controller 1133 may provide the interrupt controlcommand CTRL to the storage device 1200 to adjust the number ofgenerated interrupts.

FIG. 9 is a conceptual diagram illustrating operations of the submissionqueue and the completion queue shown in FIG. 4.

Referring to FIG. 9, the submission queue (SQ) 1134 includes first tom^(th) submission queues SQ1 to SQm. An IO request received from the CPU1110 is stored in the first to m^(th) submission queues SQ1 to SQm. Thecompletion queue (CQ) 1135 includes first to n^(th) completion queuesCQ1 to CQn. Completion information received from the storage device 1200is stored in the first to n^(th) completion queues CQ1 to CQn. Thenumber of delayed IOs may be obtained through the submission queue (SQ)1134 and the completion queue (CQ) 1135.

The decision maker 1132 may decide an interrupt control level ICL basedon the number of the delayed IOs. Equation (1) shows the procedure ofdeciding the interrupt control level ICL using the number of delayedIOs. It will be assumed that a submission queue IOsq is 100 (m=100) anda completion queue IOcq is (n=10).P1=IOsq−IOcq  Equation (1)

The decision maker 1132 may utilize Equation (1) to calculate the numberof delayed IOs (P1) using a difference between a submission queue SQ anda completion queue CQ (IOsq−IOcq). In the Equation (1), the number ofthe delayed IOs is 90.P2=P1/2  Equation (2)

The decision maker 1132 may utilize Equation (2) as a decision functionfor obtaining an interrupt control level ICL. According to the Equation(2), a decision function (P2) is 90/2. That is, the interrupt controllevel ICL is 45. When the interrupt control level ICL is 45, the storagedevice 1200 omits interrupt generation of 45 times and may generate aninterrupt only once.P3=P2%(windowsize)  Equation (3)

The decision maker 1132 may utilize Equation (3) as a decision functionfor obtaining an interrupt control level ICL using a modular operation.It will be assumed that a window size is 24. The decision maker 1132performs a modular operation on the P2 obtained in the Equation (2) tocalculate the interrupt control level ICL. The decision maker 1132 mayreduce interrupt generation of the storage device 1200 through theinterrupt control level ICL.

The storage device 1200 may receive the interrupt control command CTRLto adjust interrupt generation. The storage device 1200 fetches an IOrequest from the submission queue (SQ) 1134 and executes the IO request.After completing the IO request, the storage device 1200 sends aninterrupt to the completion queue (CQ) 1135 according to the interruptcontrol command CTRL.

FIG. 10 is a table defining a delay IO shown in FIG. 9.

Referring to FIG. 10, the delayed IO may be defined in various manners.A first delayed IO may be defined using the number of submission queuesSQ. In the example of FIG. 9, the first delayed IO may be m. A seconddelayed IO may be defined using the number of completion queues CQ. Inthe example of FIG. 9, the second delayed IO may be n. A third delayedIO may be defined using the sum of the submission queue SQ and thecompletion queue CQ (IOsq+IOcq). In the example of FIG. 9, the thirddelayed IO may be m+n. A third delayed IO may be defined using adifference between the completion queue SQ and the completion queue CQ(IOsq−IOcq). In the example of FIG. 9, the fourth delayed IO may be m−n(m>n).

FIG. 11 is a block diagram of a computer system 2000 according toexample embodiments of inventive concepts.

Referring to FIG. 11, as illustrated, the computer system 2000 mayinclude a host 2100 and a plurality of storage devices 2210 to 2230. Thehost 1100 may include a plurality of central processing units (CPUs)2111 to 2113 and a plurality of adaptive interrupt control units 2131 to2133.

A first AIC unit 2131 may detect a load status of the first CPU 2111.The first AIC unit 2131 may decide an interrupt control level ICL basedon the number of delayed IOs of the host 2100 and the first storagedevice 2210. The first AIC unit 2131 may send a first interrupt controlcommand CTRL1 to the first storage device 2210. The first storage device2210 may adjust the number of generated interrupts according to thefirst interrupt control command CTRL1. The first storage device 2210 mayreceive a first IO request REQ1 from the first AIC unit 2131. Aftercompleting the first IO request REQ1, the first storage device 2210 maysend a first interrupt INT1 to the first AIC unit 2131 according to thefirst interrupt control command CTRL1.

Similarly, the second AIC unit 2132 may send a second interrupt controlcommand CTRL2 to the second storage device 2220. After completing asecond IO request REQ2, the second storage device 2220 may send a secondinterrupt INT2 to the second AIC unit 2132 according to the secondinterrupt control command CTRL2. After completing a third IO requestREQ3, the third storage device 2230 may send a third interrupt INT3 tothe third AIC unit 2133 according to the third interrupt control commandCTRL3.

The computer system 2000 may perform adaptive interrupt control (AIC)even when the host 2100 includes a plurality of CPUs. The computersystem 2000 may efficiently decrease the number of generated interruptsthrough the adaptive interrupt control (AIC).

FIG. 12 is a block diagram of a computer system 3000 according toexample embodiments of inventive concepts.

Referring to FIG. 13, as illustrated, the computer system 3000 includesa host 3100 and a storage device 3200. The host 3100 includes a centralprocessing unit (CPU) 3110, a random access memory (RAM) 3120, a devicedriver 3130, and an external memory interface 3140.

The CPU 3110 may control the overall operation of the host 3100. The RAM3120 may be used to drive an operating system (OS) or the device driver3130. The device driver 3130 may be software to drive the storage device3200. The external memory interface 3140 may be connected to the storagedevice 3200 through an external bus.

The storage device 3200 includes a flash memory 3210, a memorycontroller 3220, and an adaptive interrupt controller 3230.

The storage device 3200 may be a high-speed storage device based on theflash memory 3210. When the storage device 3200 performs an IO operationat high speed, an overhead may occur in the host 3100 due to too manyinterrupts.

In some example embodiments, the memory controller 3220 may execute asoftware module such that the memory controller 3220 performs theoperations of the AIC controller 3230. In other example embodiments, theAIC controller 3230 may be a dedicated processor and/or circuit designedto perform the same.

The adaptive interrupt controller 3230 may adjust interrupt generationof the storage device 3200. The adaptive interrupt controller 3230 mayadjust interrupt generation through the number of delayed IOs during anIO operation of the host 3100 and the storage device 3200. The adaptiveinterrupt controller 3230 may include the decision maker 1132 and theinterrupt controller 1133 shown in FIG. 4.

The adaptive interrupt controller 3230 may calculate the number ofdelayed IOs using a submission IO IOsq and a completion IO IOcq. Theadaptive interrupt controller 3230 may calculate an interrupt controllevel ICL using the number of delayed IOs. The storage device 3200 mayadaptively control interrupt generation using the interrupt controllevel ICL. The computer system 3000 shown in FIG. 12 includes anadaptive interrupt controller 3230 in the storage device 3200. Thecomputer system 3000 may adaptively adjust the interrupt generationusing the adaptive interrupt controller 3230 to secure a CPU gainwithout loss of performance or processing time of the computer system3000.

The computer system 3000 shown in FIG. 12 may include a load watcher1131 (see FIG. 4) in the device driver 3130 of the host 3100. The devicedriver 3130 may periodically check a CPU load status. The device driver3130 may activate adaptive interrupt control (AIC) using an idle ratioof the CPU.

The computer system 3000 may include an adaptive interrupt controller3230 in the storage device 3200. In addition, the computer system 3000may include a load watcher in the device driver 3130. The computersystem 3000 may adaptively control interrupt generation of the storagedevice 3200 based on a load status of the CPU or the number of delayedIOs. The interrupt generation of the storage device 3200 may be adjustedto secure a CPU gain without loss of performance or processing time ofthe computer system 3000.

As described above, a computer system according to example embodimentsof inventive concepts may control interrupt generation of a storagedevice based on a load status of a CPU or the number of delayed IOs. Theinterrupt generation of the storage device may be efficiently adjustedto enhance performance of the computer system.

The above-disclosed subject matter is to be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other features, which all within thetrue spirit and scope of inventive concepts. Thus, to the maximum extentallowed by law, the scope of inventive concepts is to be determined bythe broadest permissible interpretation of the following claims andtheir equivalents, and shall not be restricted or limited by theforegoing detailed description. While some example embodiments have beenparticularly shown and described, it will be understood by one ofordinary skill in the art that variations in form and detail may be madetherein without departing from the spirit and scope of the claims.

What is claimed is:
 1. A computer system comprising: a storage deviceconfigured to receive an input/output (IO) request, and to send aninterrupt after completing the IO request, the interrupt indicating thatan IO associated with the IO request is an IO completion; and a hostconfigured to, generate the IO request, tally a number of the IO requestsent by the host, and a number of the IO completion by the storagedevice, determine a number of delayed IOs based on the number of the IOrequest and the number of the IO completion, calculate an interruptcontrol level based on the number of delayed IOs, and selectively adjusta frequency of the interrupt from the storage device in response to theinterrupt control level being greater than a threshold, wherein the hostis configured to selectively transmit an interrupt control command tothe storage device in response to the host determining that theinterrupt control level is greater than the threshold, and the storagedevice is configured to adjust the frequency of the interrupt based onthe interrupt control command.
 2. The computer system as set forth inclaim 1, wherein the host comprises: a memory including, a submissionqueue configured to store the number of the IO request generated by thehost, and a completion queue configured to store the number of the IOcompletion completed by the storage device.
 3. The computer system asset forth in claim 2, wherein the host is configured to calculate thenumber of the delayed IOs as a sum of the number of IO requests storedin the submission queue and the number of IO completions stored in thecompletion queue.
 4. The computer system as set forth in claim 2,wherein the host is configured to calculate the number of the delayedIOs as a difference between the number of IO requests stored in thesubmission queue and the number of IO completions stored in thecompletion queue.
 5. The computer system as set forth in claim 1,wherein the host is configured to, monitor a load status of a centralprocessing unit, and selective adjust the frequency of the interruptfrom the storage device based on the load status and the number of thedelayed IOs.
 6. The computer system as set forth in claim 5, wherein thehost is configured to activate an adaptive interrupt control of thestorage device based on an idle ratio of the central processing unit anda threshold.
 7. The computer system as set forth in claim 5, wherein thehost is configured to adjust the frequency of the interrupt by,selectively sending the interrupt control command to the storage devicebased on the interrupt control level.
 8. The computer system as setforth in claim 7, wherein the host is configured to determine a loadstatus of the central processing unit.
 9. The computer system as setforth in claim 8, wherein the host is configured to execute a devicedriver to drive the storage device.
 10. A computer system comprising: afirst storage device configured to receive a first input/output (IO)request, and to send a first interrupt after completing the first IOrequest, the first interrupt indicating that a first IO associated withthe first IO request is a first IO completion; a second storage deviceconfigured to receive a second IO request, and to send a secondinterrupt after completing the second IO request, the second interruptindicating that a second IO associated with the second IO request is asecond IO completion; and a host including a first processor and asecond processor, the host configured to, perform adaptive interruptcontrol of the first processor by, tallying a number of the first IOrequest sent by the host, and a number of the first IO completion by thefirst storage device, determining a number of delayed first IOs based onthe number of the first IO request and the number of the first IOcompletion, calculating a first interrupt control level based on thenumber of delayed first IOs, and selectively adjusting a frequency ofthe first interrupt from the first storage device in response to thefirst interrupt control level being greater than a first threshold, andperform adaptive interrupt control of the second processor by, tallyinga number of the second IO request sent by the host, and a number of thesecond IO completion by the second storage device, determining a numberof delayed second IOs based on the number of the second IO request andthe number of the second IO completion, calculating a second interruptcontrol level based on the number of delayed second IOs, and selectivelyadjusting a frequency of the second interrupt of the second storagedevice in response to the second interrupt control level being greaterthan a second threshold, wherein each of the first processor and thesecond processor is configured to selectively send an interrupt controlcommand to the first and second storage devices based on the firstinterrupt control level and the second interrupt control levelrespectively.
 11. The computer system as set forth in claim 10, whereinthe host is further configured to monitor a load status of the firstprocessor and the second processor.
 12. The computer system as set forthin claim 11, wherein the host is configured to, activate the adaptiveinterrupt control of the first storage device based on an idle state ofthe first processor and the first threshold, and activate the adaptiveinterrupt control of the second storage device based on an idle state ofthe second processor and the second threshold.
 13. A host devicecomprising: an interface configured to communicate with a storagedevice; and a processor configured to selectively activate adaptiveinterrupt control (AIC) based on one or more of an idle ratio associatedwith the host device and a number of delayed interrupts (IOs), theprocessor configured to selectively activate the AIC by, tallying anumber of IO requests sent by the host device, and a number of IOscompleted by the storage device, determining the number of delayed IOsbased on the number of IO requests and the number of IOs completed,calculating an interrupt control level (ICL) based on at least thenumber of delayed IOs, and selectively instructing the storage device toperform the AIC, if the ICL is greater than a threshold, the interruptcontrol command instructing the storage device to reduce a number ofinterrupts transmitted to the host device, wherein the processor isconfigured to, determine an idle ratio associated with the host devicebased on a load status of the processor, and calculate the ICL based onthe idle ratio and the number of delayed IOs.